Liquid level indicating device



Feb. 1o, 1959 d l.. BODDY 2,873,305

LIQUID LEVEL INDICATING DEVICE United States Patent() 2,873,305 LIQUIDLEVEL INDICATING DEVICE Leonard Buddy, Ann Arbor, Mich., assignor toKing- Seeley Corporation, Ann Arbor, Mich., a corporation of Michigan 1Claim. (Cl. 174-52) This invention relates to current modulating devicesand more particularly to variable-impedance, fluid-levelmeasuringdevices.

The object of this invention is to improve, simplify and reduce the costof manufacture and maintenance of fluidlevel measuring devices.

A feature of this invention is sive to variations in the level value ofa resistance.

Another feature of this invention is a movable lever carrying aresiliently mounted electrical contact adapted to engage and control theresistance of a resistive element.

Another feature of this invention is an improved means for limiting themotion of a lever controlling the value of a variable resistor.

A further feature of this invention is an improved means for insulatingan electrical terminal from a casing carrying electrical components.

The manner of accomplishment of the foregoing object, the nature of theforegoing features, and other objects and features of the invention, maybe perceived from the following detailed description of an embodiment ofthe invention when read with reference to the accompanying drawings inwhich:

Figure l is a diagrammatic view of a gauging system with which thecurrent modulating device constituting this invention may be embodied;

Fig. 2 'is a view in bottom plan of an improved rheostatic elementadapted to respond to the level of a fluid, embodying the principles ofthe invention;

Fig. k3 is a view in vertical section of the structure of Fig. 2; and lFig. 4 is a view in vertical section, taken substantially along the line4 4 of Fig. 3. j

This' application is a division of my application Serial No. 108,773,filed August 5, 1949, now Patent No. 2,835,885, granted May 20, 1958,relating to Thermal Responsive Gauging System. Details of the operationof the gauging circuit, of which the device constructed in accordancewith the principles of the present invention may be a part, arepresented in the aforesaid application and reference may be had theretoto supplement the general description hereinafter presented.

Considering first the system of Fig. 1, in general, the i-llustrativegauging circuits 10, 12 and 14 are connected in parallel with each otherand receive electric energy, at a voltage regulated by regulator 16,from a source 18. The source 18 may be of various types, but when thepresent improvements are used in connection with automotive vehicles,source 18 may, for example, comprise a usual engine driven generator 20and a battery 22. In line with conventional automotive practice, vavoltage regulator VR is interposed between the generator and the batteryand, as will be understood, serves to maintain the voltage of the latterbetween limits which are acceptable for many of the vehiclerequirements. In practice, these limits are not close enough forsatisfactory operation of desirably simple electric gauges.

-Theregulator-16receives the noticeably variable outan improved meansresponof a iluid for varying the ICC put of the source 18 and deliverspulsating energy to theV l gauging circuits,

the effective voltage of the regulator being substantially independentof variations in the voltage of the source. Under these conditions, itwill be appreciated that the individual gauging circuits can utilizesimple rheostatic elements 24, 26, and 28 which, in response to liquidlevel, engine temperature, oil pressure, or other physical condition,serve to vary the resistance of the individual gauge circuits andthereby control the current through, and consequently the positions of,the individual gauges 30, 32, and 34.

As diagrammatically shown in Figure l, the regulator 16 comprises athermally responsive tri-metallic element 40, which carries a heaterwinding 42. One terminal of winding 42 is grounded as indicated, and theother ter minal thereof is electrically connected to the element 40. Inthis instance the current modulating means comprises a pair of contacts44 and 46 and a shunt resistor 70. The element 40 carries the movablecontact 44, which normally engages the xed contact 46. Contact 46 inturn is connected to the source 18 through a control switch 48 whichmay, for example, be controlled concurrently with or be a part of theignition switch of the associated vehicle.

With this relation, it will be appreciated that closure of switch 48completes the circuit from the source 18, through contacts 46-44, thebody `of the element 40 and the heater winding 42 to ground. Completionof this circuit supplies heat to the element 40 and causesitstemperature to rise. As is discussed in more detail below, theelectrical resistance of the element for all practical purposes, all ofthe be considered as being derived from the winding 42. With thisrelation, element 40 can also serve as a con ductor of the gauging andheating currents.

Upon being heated, the element 40 warps and separates the contacts 44and 46, interrupting the just traced circuit and also reducing theheating effect to a value determined by shunt resistor 70. The reductionin heating effect enables the element 40 to cool and restore thecontacts 44-46 to closed condition. So long, accordingly, as switch 48remains closed, contacts 44-46 are periodically opened and closed andthe heating current is correspondingly modulated. Consequently, theelement 40 acquires a temperature just high enough to hold the contacts44-46 n a condition of incipient closing and opening. Consequently,neglecting ambient eiTects, regulator 16 acts to receive from the source18 an amount of electric energy, in pulsating form, which has asubstantially uniform heating value. On this basis, and since, over anyperiod of time, the wattage input to the regulator heater (E2/r) is at aconstant rate, it is evident that the regulator 16 breaks up the energysupplied by source 18 into a succession of pulses having an effectivevoltage which is independent of variations in the voltage of the source18.

The voltage impressed across winding 42, between terminal 44 and groundis, of course, equal to the voltage impressed upon the individualgauging circuits 10, 12, and 14. These circuits, therefore, are suppliedfrom the source 18 with pulsating energy at an effective voltage whichis substantially independent of variations in the voltage of the source18. Regulator 16 thus effectively serves as a regulator of the voltageimpressed across the gauging circuits, and currents drawn lby theindividual gauging circuits are thus independent of variations in volt-vage of the source 18.

The liquid level unit 24 in Figure 1 is diagrammatically shown ascomprising a resistor 50 disposed to be variably engaged by a groundedcontact 52 which in turn is suitably connected to a float 54. As theliquid level-rises, the' 40 is so low that'. heating effect can'correspondingly reduced, which action, of course, increases the currentdrawn by the -corresponding indicator 30. This current increase raisesthe temperature of its associated bimetal` and causes a correspondingtravel of the gauge needle. A reverse Aaction is, of course, caused bythe lowering-of' the liquid level.

' Referring now tojFigures 2, 3 and 4, a preferred construction ofliquid level unit 24 is illustrated asv compris- `ing a' main casingportion 130 composed of a cup-shaped stampingl 132 and a cover 134therefor. Casing 130 is carried by a mounting plate 136, which isadaptedto be permanently secured in place ontheassociated'liquid'containe'r such as the gas tank-of an automobile.

The wall of the cup-shaped casing member 132'isapertured' to receiveav-bearing element-'133, which rotatably journals a` crank 140, theexposed portion of which is 'dapted for connection in any suitablemanner, to a oat (not shown). A triangular shaped stop member 142 is'also carried by the casing portion 132,-and is provided Withsho'ulder's144 and 146, which act as limits to the up and down swinging movementsof the arm 149. .The

parts are shown in the nearly fullV position, the low level positionbeing indicated by ldotted lines.

The inner crank arm 148 carries the previously identi- Y iied contact52, which is mounted at the free end of a spring-like supporting member15G. Member 15d in turn is riveted or otherwise permanently secured tothe crank arm 148. Contact 52'is electrically grounded by a exiblegrounding strip 152, the free end whereof is secured tothe wall of thecasing member 132 by a rivet 154. Rivet 154 also serves as a mountingfor one end -of a resisto'r` mounting member 169 of arcuate form. Theother end of. mounting member 160 is securedto the terminal s'tud 1672.Mounting member 160 carries a spirally Wound piece of resistance wireone end of which may, if desired, be grounded to the casing 'by' rivet154 and the other end whereof is electricallyl connected" to the stud162. Y

More particularly, mounting member 160 comprises a Bakelite or otherinsulating backing member 161 and an Y inner'winding carrying member163. The upper endsof elements 161-163 are apertured' to iit over thereduced inner end of the stud 162. This inner end of stud 162 is headedover, clamping elements 161-163, as well as the end of' resistor 50,between conductive washers 165 and The rheostatic and crank elementsofthe liquid level unit are, of course, initially assembled within thecasing portion 132, and this subassembly is connected to the Y eluded inthe continuously and at random, but has an average posltion mountingplate 136 by threading nut 172 onto the terminal stud 162. Beforeapplication of the cover 134, the unit is tested and adjusted so as toinsure that for given oat positions, contact 52 engages resistor 50 atthe proper point. These adjustments are readily made by bending theinner crank arm 143. The assembly isi completed by applying the cover134, which is held in place by bending over one or'moreears 176 providedon the case.

it' will be' noted that theoat arm 140 may be subject to rapidlyiiuctuating positions in operation which movements are, of course,communicated to the associated rheostat contact 52. Thus, the value ofresistor 50 inl liquid level unit circuit varies more or Vless which isa measure of the height of the liquid in the container. These rapidlyfluctuating and' random variations Yin the value of resistor 5i? have nonoticeable eiect upon the position of the needle of the correspondingindicator Sii, in View of the thermal lag embodied in the latter.

Whileit will be apparent that the embodiment of thel invention hereindisclose-d is well calculated to fulfill the objects above stated, itwill be appreciated that the invention is susceptible to modification,variation and change" without departing Yfrom the proper scope or fairmean; ing of the subjoined claim.

What is claimed is:

in a device for modulating electrical energy in accordance' with thefuel level in a fuel tank having anaperture therein, a generallycup-shaped casing havingv an aperture therein, electrical energymodulating means withink and supported by said casing', a mounting platehaving a central cavity defining a plurality of wall portions andadapted to be secured to the fuel tank over the aperttuel therein, athreaded stud electrically connected to said 167,V thus completing themounting for the resistor 50 Y and also electrically connecting it tothe stud" 162.

The aligned aperturesl in the casing member 130 and the mounting platev136 receive, respectively, insulators 169 and171. TheI outer peripheryof' insulator 169 is non'- circular, and-a; nonrotative connectionbetween it and casing member: 132 is afforded by striking one or moretongues132a' from the body'of the latter. The innerperiphery ofinsulator 169 is polygonal and receives the corrr-:spondingly-shapedportion of stud 162. Insulator`171 mayl be'andI preferably is formedV ofa syntheticv material which normally formsV a tight seal around thestud, but' whichf.- tends to swell and increase` theeiectiveness ofthe'seal in the event gasoline or similar liquids comel in cou-Y tact withit. Externally of the casingv an insulating washer-173 is interposedbetween mounting plate 136 and' the' clamping nut 172 which is threadedonto terminal 162. With this-relation, it will be appreciated thattermitral-,162 is electrically connected to one`V end of re`` sistor'but that these elements are insulated from the housing exceptthrough'conta'ct 52. TheseV elements may beiy additionally electricallyconnectedY to the housing. thrug'lllrivet 154;, in.- the event thelower' eudof theiresistor Suis-connected to thelatter;

" of course,

The mounting plate 136, has a fluid-tight connectionwith. the liquidcontainer, butY the balance-.of

the liquid level unit is not required to; be liquid-tight.Consequently,.no provision need` be. made for sealing` thecraulsbearing;

means and supported by said' mounting plate, a; nut threadedly engagingsaid stud for securing said stud to' said mounting plate, insulatingmeans disposed between said nut and said mounting plate for insulatingsaid nut from said mounting plate, an insulating washer engaging' theaperture in said casing and said stud and insulating said stud from saidcasing, means preventing rotation of saidwasher relative to said casing,means preventing rotation of said stud relative to said washer, meansincluding said stud for securing said casing to and 1n direct'mechanical and electrical engagement with said mountingA plate,- aportion of said casing seating withln'the central cavity in saidmounting plate and Vlying above the level of the aperture-in the fueltank, means includingsaid wall portions for hiring said casing inposition relav tiveto said mounting plate, cover plate means cooperatingwith said' casing to enclosemsaid electrical energy modulating means, aportion ofV said cover plate meansbeing disposed between said casing andone off said wallportions, and meansv forV detachably securing saidcover'I plate means. to said casing, said cover plate beingremovablefrom said casing whilesaid casing is securedvv to said mounting plate.

Y References Cited in the file of this patent Sweden Octf29; 1940

